Evaluation of a composite stilbene for the fast neutron detection

Stilbene is one of the representative scintillator for the fast neutron detection and also the powerful tools to estimate the neutron-yield evolution with a high temporal resolution against the background of accompanying gamma rays in experiments with non-stationary neutron sources. It demonstrates very high capability of neutron-gamma pulse shape discrimination and could provide high gamma-ray suppression that is essential for fast neutron spectrometry. However, the size of single crystal stilbene is limited due to the difficulties in the growing technology. In order to apply an effective and convenient detection technique for various neutron field measurement, we have developed a large area composite stilbene scintillator with a dimension of Φ 200 mm × 20 mm which was obtained from the grains of stilbene crystal. Crystalline grains of stilbene have been preliminarily obtained by mechanical grinding of stilbene single crystals, and a large size composite stilbene scintillator was manufactured with crystal grains into organosilicone base. A neutron tagger module was used for the signal digitization, which consists of Flash-ADC and FPGA implemented with real-time n-γ separation processor by using a charge comparison method. The neutron sources used for this study are Cf-252 and mono-energy fast neutrons by using the accelerator in Korea Institute of Geoscience and Mineral Resources (KIGAM). The detection and separation performances for gamma-ray and neutron were evaluated and compared with the single crystal stilbene and BC-501A liquid scintillator. The result shows that the detector could be possible to apply various fields for fast neutron detection.